Skip to content
Elisabeth C. Miller Library

Archives: Plant Answer Line Q & A

Plant Answer Line questions and answers.

Growing kiwi

I have two very healthy kiwi vines, one male and one female. My female plant is flowering profusely right now, but there are no flowers on the male plant. I have had the plants for about 15 years or more and have never had fruit. They do not seem to bloom at the same time. I have just never bothered about it before, but this year I thought I would check out some options.

Any resources regarding hand pollination (both instructions and local suppliers) would be really helpful.

Oregon State University Extension’s guide, Growing Kiwifruit by Bernadine Strik (2005), has information about pollination:

“For fruit to be produced, male and female vines must be present in a block and must flower at the same time. Male flowers produce viable pollen for only the first 2 to 3 days after opening. However, female flowers are receptive to pollen for 7 to 9 days after opening, even when the petals have started falling.

“Pollination is extremely important in kiwifruit production. Large fruit contain 1,000 to 1,400 seeds (research on Hayward). If pollination is poor, fruit will have indentations (narrow valleys) on one side or be non-uniform in shape. If you cut through these fruit, you will find no seeds in these areas.

“Kiwifruit flowers are pollinated mainly by insects, although wind may play a minor role. Honey bees are the main pollinator used in kiwifruit vineyards. Kiwifruit flowers do not produce nectar and are relatively unattractive to bees. About three to four hives per acre are needed to adequately pollinate kiwifruit. Place these in the vineyard no sooner than 10 percent bloom of the female vines.

“In some years, you may have no male vines in flower as a result of winter injury to male plants (they are less hardy than the females). In this case, no naturally produced pollen will be available. To get a crop, the females will have to be pollinated artificially. Call your county Extension agent for more information on sources of pollen and methods of artificial pollination.”

(Note the section on Hardy Kiwi which are different than Fuzzy Kiwi.)

You might also find this article from The Olympian newspaper (May 16, 2009) of interest. It features kiwi growers Hildegard Hendrickson and ‘KiwiBob’ Glanzman, and discusses hand pollination, general care, pruning and training.

,

Grass-carrying wasps

Who has moved into the tubes in my mason bee house? There are these strange bundles that seem to have dead crickets entombed in them. Do I need to remove them?

 

Your description and photos convince me that these bundles were made by grass-carrying wasps (Isodontia species) who store food (such as crickets!) with their cocoons to nourish the larvae when they emerge. Your mason bee house was a convenient location to nest. They look for any hollow cavities (such as stems, trees, or even window tracks), and the mason bee tubes were a perfect spot.

They would have built the nest in early summer, emerging later (late July through September) to visit flowers for pollen and nectar.

Grass-carrying wasps are beneficial insects just like mason bees, and serve as pollinators, too. This article from Heather Holm’s Restoring the Landscape with Native Plants (author of Bees: An Identification and Native Plant Forage Guide, 2017) mentions them visiting Solidago, Eupatorium, and Plantago.

As far as removing the grass-shrouded crickets or katydids, I would follow your normal mason bee housecleaning schedule. Usually, cleaning the tubes would be done between October and December. This page from David Suzuki’s web page describes the process.

If you are curious to see a grass-carrying wasp in action, entomologist Michael Raupp’s Bug of the Week page includes a video of a wasp creating its nest.

, ,

Trees to attract hummingbirds

We have a dead cherry tree in front of our house. We’re sad that it died since birds loved it and it bloomed starting early winter. We’d like to find someone to replace it for us and we’d like the new tree to be small to medium in size and be a draw for hummingbirds and other birds as the old cherry tree was.

What tree would you recommend to replace our old cherry tree?

 

We recommend you select a certified arborist to remove the dead tree. There is a list online here where you can narrow a search to your area.

There are some evergreen, flowering shrubs which appeal to hummingbirds, such as Grevillea, which can reach 8 feet tall, depending on the variety. Arctostaphylos (Manzanita) species and Abelia grandiflora are also possibilities.

Trees which are attractive to hummingbirds (according to Welcoming Wildlife to the Garden, by Catherine Johnson and Susan McDiarmid, 2004) include Malus species (crabapple), Crataegus (hawthorn), and Sorbus sitchensis (Sitka mountain ash).

Here are some websites with more suggestions:
Backyard Wildlife Habitat
WA Dept. of Fish and Wildlife Backyard Wildlife Sanctuary
USDA National Resources Conservation Service’s Backyard Conservation tips

,

Mystery trees of Tel Aviv

Sometimes reference librarians ask ourselves questions—especially in times of social isolation! Since libraries are closed, I have been rereading my own collection of books. When I Lived in Modern Times is a novel by Linda Grant, set in 1940s Tel Aviv before Israel became a state. The main character refers several times to unnamed trees that are growing along Rothschild Boulevard (Sderot Rothschild). The trees are noteworthy, yet she cannot identify them. After having read this book twenty years ago, I decided it was time to solve the mystery!

 

[mysterytrees] cover

By searching Google Maps, I could see there were two main types of trees. It’s a mile-long road with a central pedestrian thoroughfare, and in researching sources like Tel Aviv municipal archives and local news, I determined that both Delonix regia and Ficus (F. microcarpa and F. sycomorus) grow there. Delonix, native to Madagascar, was introduced to Israel in the 1920s and may have been planted on the boulevard then or later. The trees are depicted in a 1937 painting by Yehezkel Streichman, “The Kiosk on Rothschild Boulevard.” The ficus trees on Rothschild Boulevard were planted in the 1930s. Although jacaranda trees are mentioned in various historical sources, I did not see contemporary images of them, though a 1946 photo of Rothschild Boulevard at the intersection of Allenby Street (the very corner mentioned in Grant’s novel) shows jacaranda and ficus branches overhanging a photographer’s sidewalk photo-shoot.

Tel Aviv’s founders—with one exception—believed they could ‘make something from nothing’ (yesh me’ayin) of this sandy location. The lone dissenter thought it folly and, in a 1909 photo celebrating the city’s founding, he stands far apart from the others, atop a distant dune, possibly still muttering ‘crazy people, there’s no water here’ (meshuga’im—ayn kan mayim!).

Rothschild Boulevard was built in 1910, utilizing a sand-filled wadi (dry riverbed) which was not stable enough for buildings. The street’s original name was Rehov Ha’Am, Street of the Nation (or the People). Cypresses formed the outline of the boulevard’s edges, with grass and flowerbeds in the middle.

The city’s first mayor Meir Dizengoff had grand and somewhat impractical urban planning ideas. He wanted to impress Winston Churchill (who was due for a visit in 1921) by creating a tree-lined boulevard to rival any in Europe. Mature trees were transplanted from nearby locations, but they did not have time to establish themselves in the arid soil. When people thronged to see Churchill, some climbed the trees, toppling them. Churchill reportedly said, “That which has no roots is bound to wither,” a sly, barbed remark, coming from the man who was Secretary of State for the Colonies during the period of the British Mandate in Palestine.

In 1925, Patrick Geddes, a Scottish botanist and town planner, produced a plan for Tel Aviv. He envisioned a “garden city,” with a blend of “mainways” (for vehicles) and “homeways” (residential interior streets), and a series of east-west green boulevards to connect key urban sites, so the city would have a strong sense of nature.

To this day, Rothschild Boulevard is a well-used tree-lined corridor through the heart of a busy city. Just as we have cherry blossom mania in spring here in Seattle, there is great excitement when the red flowers of Delonix regia (known as flame tree, Royal Poinciana, Flamboyant, Gulmohar, and in Hebrew tze’elon naeh) bloom in early June. The ficus trees with their pale trunks sometimes covered in a net of accessory trunks made of aerial roots, are stately but drop fruit that can be perilous for pedestrians. Still, they are a notable feature of the landscape; Tel Aviv-Yafo municipal agronomist Haim Gavriel even published a recent monograph about the Ficus of Israel’s Boulevards.

Resources that were useful in researching this mystery include:

  • Mann, Barbara. A Place in History: Modernism, Tel Aviv, and the Creation of Jewish Urban Space. Stanford University Press, 2006. [accessed online 4/25/2020]
  • Mann, Barbara. “Tel Aviv’s Rothschild: When a boulevard becomes a monument.” Jewish Social Studies, New Series, Vol. 7, No. 2 (Winter, 2001), pp. 1-38. [accessed online 4/24/2020]
  • Rosenberg, Elissa. “Tel Aviv never stops.” Landscape Architecture Magazine 107 (11), 120-128
, , ,

Snowdrop buds won’t open

I planted some Galanthus ‘Flore Pleno’ three years ago. For all three years, the foliage comes up, buds form…..and then nothing. The buds swell and begin to color, but they never ‘drop,’ and will remain on the plants for up to two months without change. They never open, but very gradually become desiccated. They do not turn brown like daffodils with bud blast, and I see no signs of fungal disease. The foliage appears totally healthy. They are planted in a north facing bed, soil is medium-heavy but not waterlogged. I have done research but have found no explanation. Any thoughts are appreciated.

 

A general article by Christopher Lloyd on snowdrops in The Guardian (2001) makes a brief mention of heat causing bulbs to go blind (i.e., not flower), but this is said in the context of growing them indoors. Lloyd also mentions that Galanthus bulbs “are at their happiest in a clay/humus-rich soil that will be damp in winter and spring and dry during the summer.” They do not thrive in soil which is too rich or too acidic.

Another possibility is that you may need to divide them. Seattle’s Dunn Gardens has a helpful care sheet for growing snowdrops. Here is an excerpt:
“In the garden snowdrops do best in a partially shaded situation. If you have a very sandy, free-draining soil, amend it with compost. They love damp ground especially in the winter/spring. After the plant has finished flowering, allow the foliage to fully die down on its own. Do NOT cut the foliage off early, nor twist or braid it. Yes it will be ugly, but if planted around later emerging perennials, it won’t be so offensive.
“The Narcissus fly is the bane of snowdrops. After flowering, the fly will lay eggs on the foliage. The eggs hatch and the maggots will eat their way down into the bulb, destroying it. We’ve found that siting this bulb, where it gets afternoon or full shade after flowering, greatly reduces the chances of infestation. There is little in the way of chemical control, and what there is, is nasty.
“To bulk up galanthus, liquid feed after flowering, with a half strength solution of a water-soluble fertilizer, every two weeks, until the foliage has died down completely. If you
notice that the clumps are becoming congested (bulbs are starting to push up out of the ground), divide immediately after flowering.”

I recommend Naomi Slade’s book, The Plant Lover’s Guide to Snowdrops (Timber Press, 2014). In it, she describes in great detail the Fibonacci series by which snowdrops multiply: some varieties do this quickly, others slowly, in a mathematically governed sequence. The result of this natural system of propagation is that you will eventually have a dense clump of snowdrops that needs splitting up every few years if the bulbs are to have sufficient resources to produce flowers.

, ,

Edible buckwheat and cushion buckwheat

What is the difference between the buckwheat plant that is used as an edible grain, and the wildflowers that are also called buckwheat? Are they related? I saw a plant growing on a ridge in the Olympic Mountains that was later identified for me as cushion buckwheat. Also, are there flowering buckwheats that people grow as ornamentals in gardens?

 

Edible buckwheat generally refers to Fagopyrum esculentum. If you were to find it growing wild in Washington State, it would be considered an escaped cultivated plant (i.e., weedy). It is sometimes grown as a cover crop, in addition to the use of its ground seeds for buckwheat flour. It is called a pseudograin or pseudocereal because it is not in the grass family (in the same way that amaranth, chia, and quinoa are pseudocereals).

Cushion buckwheat is Eriogonum ovalifolium. Like Fagopyrum, Eriogonum is in the knotweed family—Polygonaceae. There are about twenty native species of Eriogonum in Washington. Many of them grow east of the Cascades. Many more species of Eriogonum are native to California. (This article by Jennifer Jewell, Pacific Horticulture, April 2013 is a good introduction.) Many are best appreciated in the wild. If you want to grow buckwheat ornamentally, try to select a species that suits your garden conditions (ideally, in full sun, in soil that is well-drained and not overwatered, and mulched with gravel). Jewell’s article suggests that penstemon, salvia, and grasses might make good garden companions for the right species of Eriogonum. Plant expert Linda Cochran has experimented with growing a variety of Eriogonum umbellatum in her Olympic Peninsula garden.

Here is some interesting trivia about the scientific names for these different kinds of buckwheat, Eriogonum‘s name is derived from Greek: Erio = wool / gony = knee, referring to hairy nodes of the first scientifically described species E. tomentosum. Fagopyrum comes from Latin fagus (beech) and Greek pyrus (wheat) because the achenes (dried fruits) resemble beechnuts.

,

On celandine confusion

Last year I purchased a plant at a plant sale. The tag said simply ‘celandine.’ It is flowering now, and its flowers are like yellow poppies. The leaves are attractive and very distinctive—deeply cut margins, kind of like oak leaves. But when I think of celandine, I think of the Cicely Barker flower fairies books from childhood. I am not sure this is the same plant.

 

You are not alone in experiencing ‘celandine confusion,’ discussed in this article from The Scott Arboretum of Swarthmore College. The confusion rests on the use of that common name to describe a plant that is a Washington State-listed Class B noxious weed in the buttercup family, and two different plants in the poppy family.

If you remember the illustration for “The Song of the Celandine Fairy” depicting ‘the lesser celandine,’ the illustration shows Ficaria verna (also called Ranunculus ficaria). There is also a ‘greater celandine’ fairy in Barker’s books, and that image looks more like Chelidonium majus which is in the poppy family and is a native of Europe. It is a bit harder to tell the difference between Chelidonium and Stylophorum diphyllum. Your plant is most likely one of these. Other common names for Stylophorum are ‘celandine poppy,’ and ‘wood poppy.’ Stylophorum is native to moist woodlands of eastern North America. Here’s what will help you tell one from the other:
According to Andrew Bunting, curator of the Scott Arboretum, “Stylophorum has broader leaves and Chelidonium leaves are more dissected. Also, the flowers are smaller on Chelidonium.” These images from Kathy Purdy’s Cold Climate Gardening blog neatly illustrates the differences in flower and leaf size. Further, when they reach the phase of producing seed pods, the difference is striking.

For additional information about Stylophorum, including suggestions of plant combinations for gardens, see this link from University of Wisconsin-Madison’s Master Gardener Program, and this one from Bruce Crawford, director of Rutgers Gardens, on the plant that launched his career in horticulture.

, , , ,

Tulip fire

The leaves and petals of my tulips are shot through with little holes. Is this some kind of insect or a disease? And what can I do to solve the problem?

 

Your tulips may have a fungal disease called Botrytis. According to Cornell University’s Plant Disease Diagnostic Clinic, Botrytis tulipae is specific to tulips and lilies. A more colorful name for this disease is ‘tulip fire.’ Cool and damp spring or summer conditions favor the development of the disease:
“Tulip fire infections cause malformations and/or large, light tan patches on tulip leaves. These patches are most noticeable on light-colored varieties. On leaves these infections are somewhat sunken, yellow to light tan, and surrounded by a water-soaked area.
On colored petals the spots appear white and on white petals they appear brown.”

Since the fungus can overwinter in plant debris, good garden hygiene may help:

  • Clean up any diseased leaves and petals, but not when they are wet.
  • Make sure you don’t water your tulips from above (of course, you can’t stop the rain–just don’t aid and abet it).
  • Avoid congested plantings–provide air circulation around your plants.
  • Ultimately, you may want to dispose of infected plants (don’t compost).
  • Rumor has it that using a grit mulch around your tulips can be helpful as a preventive measure.

The Royal Horticultural Society advises that gardeners not plant tulips in a location where Botrytis has been present for three years. According to University of Illinois Integrated Pest Management, there is no point using fungicide where the fungus is already present, but they do describe preventive uses. Always look for the least toxic option. There are some Neem-based fungicides available for home gardeners.

An article in the Telegraph by garden writer Sarah Raven gives an excellent overview of the problem and how to manage it. She highly recommends not hesitating to remove infected plants and bulbs at first discovery, the better to keep the disease from spreading. Early tulips are less susceptible, and according to Raven, the most susceptible in her garden are Darwin tulips, while Viridiflora hybrids are unaffected. Avoid cross-contaminating lilies, fritillaries, and Juno irises by planting them at a distance from your tulips.

,

Cypress tip moth

My Leyland Cypress is browning and has Cypress tip moth signs. I’m worried about the brown spots, and wonder if it can survive this attack? How can I control the pests, if it might survive?

 

From what I can determine, your Leyland cypress (x Cupressocyparis leylandii) trees are probably going to
survive this attack unless they are weakened in some other way.
x Cupressocyparis leylandii in California survive the Cypress tip moth, though they can be unsightly. Since California is a bit too dry for this tree, the conditions are
not identical, but Natural Resources Canada does not
indicate that infestations are fatal. Because you said you found
evidence of tip moth (Cypress tip moth = Argyresthia cupressella), I will
assume that is what the problem is, but a bit of browning, even in
conifers, is not unusual right after trees are planted. Be sure that you
are not overwatering, as one effect of that is the same as underwatering
(i.e., tip die-back or yellowing) because too much water prevents the
plant from taking water and oxygen into the roots.

The Organic Gardener’s Handbook of Natural Insect and Disease Control
(ed. by Ellis and Bradley, 1996, p.183) says about pine tip moth
(Rhyacionia frustrana):

“Handpicking works if only a few caterpillars are present. Pruning off
and destroying infested tips in winter is a very effective control.”

I would recommend a prune-and-wait-and-see approach. April is a bit late to
prune (and puts root establishment in competition with shoot regrowth),
but you may be able to slow the infestation down, so go ahead and do
it. Watch the trees this season and then prune again in the winter next
year. Be sure to destroy (burn or bag and put in the garbage) the
debris so you don’t reinfect your tree.

A good gardening resource is the UBC Botanical Garden Forum. Personal
testimony/experience is valuable, especially if it’s regional. (You
might find it useful in the future.) Several people commenting about
x Cupressocyparis leylandii note that it is not a very desirable tree; one of its
parents, the Cupressus nootkatensis, also called Callitropsis
nootkatensis or Chamaecyparis nootkatensis, or, for that matter, plain Nootka cypress) is better. One person
recommended planting small trees in the beginning, since they grow very
fast. This might save you some money, should you have to replace your
trees. The site does not need a password; just click on “Search” in the upper right
corner.

Below is some additional information from Oregon State University about cypress tip moth. This site recommends pesticides, but from everything I read, they are not
effective without multiple treatments. Since this pest is generally not
fatal to the trees, it is probably not worth it to use chemicals which would be dangerous and time-consuming to apply. If you know something about the
life cycle of the pest, your observations will yield more information and any
manual control attempts are more likely to be effective.

, ,

Staking Cryptomeria japonica

I recently planted a 1 gallon, approximately 2-foot Cryptomeria japonica ‘Sekkan Sugi’ in my yard. I noticed it leans. Is it normal for it to lean? Do I need to stake it so it grows straight? If so, how I would stake it?

 

According to Oregon State University’s Landscape Plants website, Cryptomeria japonica ‘Sekkan Sugi’ is meant to be upright.

An excerpt: “Seems to be some confusion about this selection(s?), listed as both fast and slow growing. Perhaps some of the confusion can be attributed to insufficient attention in handling similar Japanese cultivar names. Jacobson (1996) lists ‘Sekka Sugi’ and ‘Sekkwia Sugi’ as synonyms for the warped and twisted cultivar, ‘Cristata’; and that ‘Sekkan Sugi’ may appear as ‘Sekhan Sugi’. van Gelderen and van Hoey Smith (1996, p 216) have a picture of a cultivar listed only as ‘Sekkan’.”

Based on what Seattle-area Great Plant Picks says about Sekkan Sugi and Cristata, I think that you may want to support your tree carefully, as both cultivars are described as upright.

An article from Iowa State University Forestry Extension (no longer available online) discusses whether or not to stake a tree:

“If possible, avoid staking and/or guying trees. Small trees, trees less than six feet tall or less than one inch in caliper or diameter, should not need staking to support them. As tree planting stock gets larger, their root system, ball-and-burlap, or pot size may not be sufficient to support them without tipping or transferring top movement down to the root system. With trees that may be able to support themselves, plant them and watch the planting hole for several days after planting. If the tree tips or leans, it needs support; if the plant stem at the soil line is moving excessively, creating a ‘crowbar’ hole which is a quarter of an inch or larger than the stem of the tree, it probably needs support.”

The book The Tree Doctor by Daniel and Erin Prendergast (Firefly Books, 2017) says that staking might be needed if your newly planted tree is in a windy or exposed location. The authors recommend anchoring the tree with at least two stakes at equal distance from the trunk. Drive the stakes into solid, undisturbed ground at least 2 feet deep, and tie the tree with biodegradable material like burlap, rather than wire encased in rubber hose. Leave at least an inch of room between each tie and the tree trunk. The tree should be able to sway in the wind. Remove the stakes and ties after a year.
I also wonder if you could carefully dig down and shift the position of the tree in its planting hole to guide it upright. If you are able to do this easily, you can avoid staking.

,